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Red Blood Cell Transfusions

Three days ago, a 65-year-old man underwent a sigmoid resection, end colostomy, and Hartman’s for a free diverticular perforation and raging peritonitis. Perioperatively the patient was aggressively fluid-resuscitated and monitored with a CVP, A-line, and Foley. Current vitals are 100/60, HR 110, and CVP 12. He remains intubated on an FiO2 of 0.6 and ABGs: Po2 100, Pco2 35, and pH 7.35. When you arrive in the SICU, this patient’s most recent urine output was 20 mL/h. The 6:00 am labs just returned, and his HCT is 24% and Hgb 8 g%.

Red Blood Cell Transfusions

Answers

This patient’s anemia is most likely dilutional, caused by his body beginning to mobilize all the fluid he received during his perioperative resuscitation 3 days prior. Still, his hemoglobin does seem low and his oliguria most likely represents some element of renal hypoperfusion. The most rapid way to increase this patient’s systemic oxygen delivery is to transfuse him with bank blood. But will that improve his overall outcome?

Goal-directed therapy (Rivers et al; see Chapter 7) protocol mandates that, following initial fluid resuscitation and inotropic support, and if the mixed venous O2 saturation remains below 70%, then transfuse blood to an Hct of 30%. But the Transfusion Requirements in Critical Care (TRICC) trial (Hébert et al) provides persuasive evidence that permitting patients to float down to an Hbg of 7 g% is safe (if not safer than transfusing at an Hbg threshold of 9 g%).

In fact, there is no controversy. Both of these beautifully conducted trials were conducted in very different cohorts of patients:

GDT patients were all in septic shock and were treated within 6 hours of admission.

TRICC patients were all documented euvolemic (normal CVP) and were randomized only after 3 days in the ICU.

So, in this case you search hard for evidence of myocardial ischemia (12-lead electrocardiogram) and in the absence of ischemia, your patient is euvolemic and has been in the ICU for 3 days. So, TRICC trumps GDT—don’t give blood yet.

When you transfuse banked blood, you are infusing much more than oxygen-carrying hemoglobin. There is a nonzero rate of infectious contamination. Also, the white cells in transfused blood are all “primed” to release toxic oxygen metabolites and proteases. Those white cells can also attack the patient, in a process called graft-versus-host disease. Leukodepletion does cut the white count by several orders of magnitude—but not to zero. And hemolyzed RBC membranes are also toxic. In our hospital, it is OK to transfuse blood that has been sitting in the refrigerator for up to 42 days. More like gymnasts than wine, banked blood does not improve with age.